Copper alloy material and method of making same

ABSTRACT

A copper alloy material for electric parts having: 1.0 to 5.0 mass % of Ni; 0.2 to 1.0 mass % of Si; 0.05 to 2.0 mass % of Sn; 0.1 to 5.0 mass % of Zn; 0.01 to 0.3 mass % of P; 0.05 to 1.0 mass % of at least one of Fe and Co; and the balance consisting of Cu and an unavoidable impurity. The ratio, (Ni+Fe+Co)/(Si+P), between the total mass of Ni, Fe and Co and the total mass of Si and P is 4 or more and 10 or less.

The present application is based on Japanese patent application No. 2005-255502, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a copper alloy material for electric parts such as a terminal, connector and lead frame and, in particular, to a copper alloy material that is excellent in mechanical strength such as tensile strength and yield strength, in elongation, in electric conductivity and in bending workability. This invention also relates to a method of making the copper alloy material.

2. Description of the Related Art

In recent years, an electronic hardware such as a cellular phone or notebook PC is downsized, low-profiled and reduced in weight. Along with this, electric and/or electronic components used therein tend to be reduced in weight, length and thickness.

In the downsizing, although materials used therein also have to be reduced in thickness, a material is needed to have a high mechanical strength, a high spring property, and a good bending workability even when it has the reduced thickness so as to keep a reliability in electric connection.

Further, generated Joule heat increases with increasing in applied current and in the number of electrodes due to the sophistication of equipment. Thus, the material is strongly desired to have a good electric conductivity than before. Such high electric conductivity is needed especially in a terminal and connector material for automobiles and a lead frame material for power IC, where the applied current tends to increase rapidly.

Conventionally, phosphor bronze is used as a material for a terminal, connector etc. However, there is a problem that the phosphor bronze cannot satisfy sufficiently the updated characteristics required to the connector material. For example, since the phosphor bronze has a low electric conductivity of about 20% IACS, it cannot be suited to an increase in applied current (i.e., it results in an increase of the generated Joule heat). Further the phosphor bronze does not have an excellent characteristic in migration resistance. Meanwhile, the migration is a phenomenon that, when a condensation of moisture occurs between electrodes, the Cu atom in the positive electrode is dissolved (ionized) and precipitated on the negative electrode, so that the short circuit between the electrodes can be caused. The phenomenon is a serious problem especially on the connector or lead frame that can be used in environment of high temperature and high humidity as in automobiles. Further, it should be considered for the connector or lead frame with an interelectrode pitch narrowed due to the downsizing.

In order to solve the above problems, copper alloys containing Cu—Ni—Si as a main component are suggested (e.g., JP-B-2572042, 2977845 and 3465541).

However, in the Cu—Ni—Si alloys, if it is intended to have a high mechanical strength and a good spring property, the bending workability is easy to deteriorate such that anisotropy in the bending process becomes significant depending on the rolling direction of the alloy strip.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a copper alloy material for electric parts, such as a terminal, connector and lead frame, that is excellent in mechanical strength such as tensile strength and yield strength, in elongation, in electric conductivity and in bending workability to show reduced anisotropy in the bending process.

-   (1) According to one aspect of the invention, a copper alloy     material for electric parts comprises:

1.0 to 5.0 mass % of Ni;

0.2 to 1.0 mass % of Si;

0.05 to 2.0 mass % of Sn;

0.1 to 5.0 mass % of Zn;

0.01 to 0.3 mass % of P;

0.05 to 1.0 mass % of at least one of Fe and Co; and

the balance consisting of Cu and an unavoidable impurity,

wherein a ratio, (Ni+Fe+Co)/(Si+P), between a total mass of Ni, Fe and Co and a total mass of Si and P is 4 or more and 10 or less.

In the above invention, the following modifications can be made.

-   -   (i) The copper alloy material comprises a tensile strength of         700 N/mm² or more.     -   (ii) The copper alloy material comprises an elongation of 10% or         more.     -   (iii) The copper alloy material comprises an electric         conductivity of 40% IACS or more.

-   (2) According to another aspect of the invention, a copper alloy     material for electric parts comprises:

1.0 to 5.0 mass % of Ni;

0.2 to 1.0 mass % of Si;

0.05 to 2.0 mass % of Sn;

0.1 to 5.0 mass % of Zn;

0.01 to 0.3 mass % of P;

0.05 to 1.0 mass % of at least one of Fe and Co;

0.01 to 1.0 mass % of at least one of Mg, Ti, Cr and Zr and

the balance consisting of Cu and an unavoidable impurity,

wherein a ratio, (Ni+Fe+Co)/(Si+P), between a total mass of Ni, Fe and Co and a total mass of Si and P is 4 or more and 10 or less.

In the above invention, the following modifications can be made.

-   -   (vi) The copper alloy material comprises a tensile strength of         700 N/mm² or more.     -   (v) The copper alloy material comprises an elongation of 10% or         more.     -   (vi) The copper alloy material comprises an electric         conductivity of 40% IACS or more.

-   (3) According to another aspect of the invention, a method of making     the copper alloy material for electric parts as defined in above (1)     comprises:

preparing a copper alloy raw material with the same composition and the same mass ratio as defined in above (1);

a first cold rolling step that the copper alloy raw material is cold-rolled down to a thickness of 1.1 to 1.3 times a target thickness of a final product;

a first heat treatment step that the cold-rolled material in the first cold rolling step is heated up to 700 to 850° C. and then cooled to 300° C. or less at a cooling rate of 25° C./min or more;

a second cold rolling step that the treated material in the first heat treatment step is cold-rolled down to the target thickness; and

a second heat treatment step that the cold-rolled material in the second cold rolling step is heated up to 400 to 500° C. and held for 30 min. to 3 hrs.

-   (4) According to another aspect of the invention, a method of making     the copper alloy material for electric parts as defined in above (2)     comprises:

preparing a copper alloy raw material with the same composition and the same mass ratio as defined in above (2);

a first cold rolling step that the copper alloy raw material is cold-rolled down to a thickness of 1.1 to 1.3 times a target thickness of a final product;

a first heat treatment step that the cold-rolled material in the first cold rolling step is heated up to 700 to 850° C. and then cooled to 300° C. or less at a cooling rate of 25° C./min or more;

a second cold rolling step that the treated material in the first heat treatment step is cold-rolled down to the target thickness; and

a second heat treatment step that the cold-rolled material in the second cold rolling step is heated up to 400 to 500° C. and held for 30 min. to 3 hrs.

<Advantages of the Invention>

A copper alloy material for electric parts, such as a terminal, connector and lead frame, can be provided that is excellent in mechanical strength such as tensile strength and 0.2% yield strength (herein called simply “yield strength”), in elongation, in electric conductivity and in bending workability to show reduced anisotropy in the bending process.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments according to the invention will be explained below referring to the drawings, wherein:

FIG. 1 is a flowchart showing a method of making a copper alloy material for electric parts in a preferred embodiment according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Composition of Copper Alloy Material for Electric Parts

Copper alloy materials for electric parts of this embodiment comprise, in average composition, 1.0 to 5.0 mass % of Ni, 0.2 to 1.0 mass % of Si, 0.05 to 2.0 mass % of Sn, 0.1 to 5.0 mass % of Zn, 0.01 to 0.3 mass % of P, 0.05 to 1.0 mass % (=total mass %) of at least one of Fe and Co, and the balance of Cu and an unavoidable impurity, wherein the ratio between a total mass of Ni, Fe and Co and a total mass of Si and P is to be (Ni+Fe+Co)/(Si+P)=4 or more and 10 or less.

The reasons for adding the alloy elements to compose the copper alloy material for electric parts and for limiting the content thereof are as follows.

The Ni, Fe and Co can be dispersed and precipitated in the material while forming a Si compound or a P compound when it is added therein together with Si and P. Although the conventional Cu—Ni—Si alloys have an enhanced mechanical strength by dispersing and precipitating a Ni—Si compound, this embodiment can have a further enhanced mechanical strength by the effects of precipitations, i.e., a Ni—P compound, and a Si compound and/or a P compound with Fe and Co in addition to the Ni—Si compound.

Thereupon, by defining the content (the addition amount) and the composition ratio of Ni, Fe, Co, Si and P to be in a specific range, the mechanical strength and spring property can be enhanced by the enhanced dispersion effect of the precipitations while suppressing the amount of solid-solution element in the Cu matrix that may reduce the electric conductivity.

If the Si is added less than 0.02 mass %, a sufficient amount of the Si compound cannot be formed and, thus, the sufficient mechanical strength and spring property cannot be obtained. If it is added more than 1.0 mass %, the electric conductivity will be badly affected and a crack may be arisen which is caused by the segregation of Si compound in the process of forming the copper alloy raw material (e.g., in the casting thereof or in the hot working after the casting). Thus, the composition ratio of Si is defined to be 0.2 to 1.0 mass %, preferably to be 0.4 to 0.7 mass %.

If the P is less than 0.01 mass %, the P compound cannot be effectively formed. If it is added more than 0.3 mass %, a crack may be arisen which is caused by the segregation of P compound in the process of forming the copper alloy raw material (e.g., in the casting thereof). Thus, the composition ratio of P is defined to be 0.01 to 0.3 mass %, preferably to be 0.1 to 0.2 mass %.

It is needed that the composition of Ni is 1.0 to 5.0 mass %, the total composition of Fe and Co is 0.05 to 1.0 mass %, and the ratio (Ni+Fe+Co)/(Si+P) between a total mass of Ni, Fe and Co and a total mass of Si and P is 4 or more and 10 or less, so as to secure simultaneously a high mechanical strength and a high electric conductivity while forming effectively the compound in relation to the above composition of Si and P. If the content of Ni, Fe and Co is less than the lower limit of the above composition, the amount of the compound formed will be insufficient, which causes a lack of mechanical strength and spring property. If the content of Ni, Fe and Co is more than the upper limit thereof, excessive Ni, Fe and Co will be dissolved into the Cu matrix as a solid solution to degrade the electric conductivity. Further, if the ratio (Ni+Fe+Co)/(Si+P) is less than 4, Si and P are excessive and if more than 10, Ni, Fe and Co are excessive by contrast. Since such an excessive component exists in solid-solution state in the Cu matrix, the electric conductivity will be degraded. It is preferably defined that the composition of Ni is 2.5 to 3.5 mass %, the total composition of Fe and Co is 0.3 to 0.7 mass %, and the ratio (Ni+Fe+Co)/(Si+P) is 4 or more and 7 or less.

Further, to the above composition, 0.05 to 2.0 mass % of Sn and 0.1 to 5.0 mass % of Zn are added.

The Sn has a significant effect to enhance the mechanical strength and spring property. Further, it has an effect to improve the stress-relaxation resistance (=heat resistance) in a temperature environment of about 150° C., and therefore it is an effective additive in the material for electric parts. However, if the content thereof is less than 0.05 mass %, the effects are not sufficient. If it is added more than 2.0 mass %, it has a negative affection to degrade the electric conductivity. Thus, the composition of Sn is preferably to be 0.05 to 2.0mass %, more preferably to be 0.3 to 1.0 mass %.

The Zn has an effect to enhance the mechanical strength and spring property. Further, it has a significant effect to enhance the migration resistance. Still further, it has an effect to improve the solder wettability and cohesion to a Sn plating which are needed in the material for electric and electronic parts. However, if the content thereof is less than 0.1 mass %, the effects are not sufficient. If it is added more than 5.0 mass %, it has a negative affection to degrade the electric conductivity. Thus, the composition of Zn is preferably to be 0.1 to 5.0 mass %, more preferably to be 0.3 to 2.0 mass %.

Second Embodiment Composition of Copper Alloy Material for Electric Parts

Copper alloy materials for electric parts of this embodiment comprise, in average composition, 1.0 to 5.0 mass % of Ni, 0.2 to 1.0 mass % of Si, 0.05 to 2.0 mass % of Sn, 0.1 to 5.0 mass % of Zn, 0.01 to 0.3 mass % of P, 0.05 to 1.0 mass % (=total mass %) of at least one of Fe and Co, 0.01 to 1.0 mass % of at least one of Mg, Ti, Cr and Zr, and the balance of Cu and an unavoidable impurity, wherein the ratio between a total mass of Ni, Fe and Co and a total mass of Si and P is to be (Ni+Fe+Co)/(Si+P)=4 or more and 10 or less.

The reasons for adding the alloy elements to compose the copper alloy material for electric parts and for limiting the content thereof are as follows.

The reasons for adding Ni, Si, Sn, Zn, P, Fe and Co and for limiting the content (=addition amount) and composition ratio thereof are the same as described in the first embodiment.

In addition, the reason why at least one of Mg, Ti, Cr and Zr is added 0.01 to 1.0 mass % in total is that additional excellent properties can be obtained. These elements have effects to improve further the mechanical strength, spring property, migration resistance, and heat resistance, and have only a small affection to lower the electric conductivity. Therefore, they are effective as an additive to facilitate the effects of the aforementioned elements in the first embodiment. However, if the total content thereof is less than 0.01 mass %, the sufficient effect cannot be expected. If it is added more than 1.0 mass %, a negative affection may appear such as deterioration in casting property in the process of forming a copper alloy raw material. Thus, the composition of Mg, Ti, Cr and Zr is in total to be 0.01 to 1.0 mass %, more preferably to be 0.1 to 0.3 mass %.

Method of Making the Copper Alloy Material for Electric Parts

FIG. 1 is a flowchart showing a method of making a copper alloy material for electric parts in the preferred embodiment according to the invention.

The above mentioned copper alloy material of the first and second embodiments can be made, after preparing the copper alloy raw material with the average composition as defined earlier, by conducting: the first cold rolling step that the copper alloy raw material thus formed is cold-rolled down to 1.1 to 1.3 times thicker than a target thickness of a final product; the first heat treatment step that the material after the first cold rolling step is heated up to 700 to 850° C. and then cooled to less than 300° C. at a cooling rate of 25° C./min or more; the second cold rolling step that the material after the first heat treatment step is cold-rolled down to the target thickness of the final product; and the second heat treatment step that the material after the second cold rolling step is heated up to 400 to 500° C. and kept for 30 minutes to 3 hours. Meanwhile, the copper alloy raw material can be, for example, prepared by conducting an alloy casting step and then a hot working step.

First Cold Rolling Step

In the first cold rolling step, the copper alloy raw material prepared is cold-rolled down to 1.1 to 1.3 times thicker than the target thickness of the final product. This process (step) promotes the recrystallization in the following first heat treatment and allows the formation of the grain structure with equalized grain size after the recrystallization. The reason why the material thickness after the rolling is defined to be 1.1 to 1.3 times the target thickness of final product is to introduce a proper amount of lattice defect such as a dislocation in the cold rolling (i.e., the second cold rolling step) after the first heat treatment step as described later. If the material thickness is more than the defined thickness, excessive lattice defects will be introduced by the cold rolling (i.e., the second cold rolling step) after the first heat treatment step and, therefore, the elongation property of the final product is lowered and the anisotropy of the elongation property is arisen depending on the rolling direction in the bending process, that causes to degrade the bending workability of the product. If the material thickness is less than the defined thickness, the lattice defect will be insufficiently introduced in the cold rolling (i.e., the second cold rolling step) after the first heat treatment step and, therefore, the mechanical strength such as tensile strength and yield strength is lowered.

First Heat Treatment Step

In the first heat treatment step, in order to carry out the solution heat treatment (solid solution heat treatment), the copper alloy material after the first cold rolling step is heated up to 700 to 850° C. and then cooled to less than 300° C. at a cooling rate of 25° C./min or more. Preferably, it is heated up to 770 to 850° C. and then cooled to less than 300° C. at a cooling rate of 150° C./min or more. Although the holding time of the heating is not defined, it is preferably shorter in consideration of the productivity and the material only has to be held at the defined temperature substantially for 1 sec. or more. The solution heat treatment in this step is intended to disperse (dissolve) uniformly the alloy component into the copper matrix so as to disperse and precipitate uniformly and finely the alloy component in the final product. Thereby, the nonuniform precipitation that may be formed in the process of preparing the copper alloy raw material can be dissolved again in the copper matrix by the solid solution heat treatment. By defining the heating temperature to be 700° C. or more, the formation of solid solution can be sufficiently progressed. By defining the cooling rate to be 25° C./min or more, a coarse precipitation (grain growth of the precipitation) can be prevented from being formed again during the cooling process.

Further, by the first heat treatment step, the grain distorted by the intensive cold working (i.e., the first cold rolling step) can be recrystallized and changed into a grain structure with less anisotropy, and the elongation property of the rolled material can be recovered to provide a good bending workability. If the heating temperature is more than 850° C., a coarsening of the grain (i.e., excessive recrystallization or exaggerated grain growth) may be occurred resulting in the degradation of the bending workability. Therefore, the upper limit of the heating temperature is defined to be 850° C.

Second Cold Rolling Step

In the second cold rolling step, the copper alloy material after the first heat treatment is cold-rolled until having the target thickness of final product. Thereby, the lattice defect which becomes a starting point (i.e., a nucleation site) for forming the precipitation in the heat treatment (i.e., the second heat treatment step) as described later can be introduced suitably into the material. Thus, the formation of uniform and fine precipitation can be promoted in the following heat treatment (i.e., the second heat treatment step), and the mechanical strength can be enhanced.

Second Heat Treatment Step

In the second heat treatment step, in order to achieve the age-hardening (precipitation-hardening), the copper alloy material after the second cold rolling step is heated up to 400 to 500° C. and held for 30 minutes to 3 hours. Preferably, it is heated up to 430 to 480° C. and held for 1 to 2 hours. Thereby, the Ni, Fe and Co can form compounds with Si and P, which can be dispersed and precipitated in the copper matrix to have simultaneously the high mechanical strength and good electric conductivity. If the treatment conditions are higher and longer than the defined range, 400 to 500° C. and 30 minutes to 3 hours, the precipitation may be coarsened to fail to have the sufficient mechanical strength. If the treatment conditions are lower and shorter than the defined range, the precipitation may be insufficiently progressed to fail to have the sufficient electric conductivity and mechanical strength.

Effects of the Embodiment

The effects of the embodiment are as follows.

-   (1) The copper alloy material for electric parts such as a terminal,     connector and lead frame can be obtained which has a tensile     strength of 700 N/mm² or more, a yield strength of 650 N/mm² or     more, an elongation of 10% or more, an electric conductivity of 40%     IACS or more, and reduced anisotropy in the bending process (i.e.,     good bending workability). -   (2) Because of the excellent properties as described in (1),     electronic parts such as a terminal, connector and lead frame can     have an expanded choice of design even when it would be downsized     all the more. -   (3) Although it has the excellent properties as described in (1), it     can be made for almost the same cost as the conventional ones.

EXAMPLES

Examples of the invention will be described below, but the invention is not limited by these examples.

Example 1 (=Sample No. 1)

A copper alloy which comprises Ni: 3.0 mass %, Si: 0.5 mass %, P: 0.15 mass %, Fe: 0.15 mass %, Co: 0.15 mass %, Sn: 1.0 mass %, and Zn: 1.5 mass % in an oxygen-free copper matrix is molten in a RF melting furnace and then cast into an ingot with a diameter of 30 mm and a length of 250 mm.

The ingot is heated to 850° C. and extruded (hot-worked) into a plate-like copper alloy raw material with a width of 20 mm and a thickness of 8 mm. Then, it is cold-rolled down to a thickness of 0.36 mm (the first cold rolling step). Then, the cold-rolled material is held at 800° C. for 10 min. and then is quenched in water to be cooled down to a room temperature (about 20° C.) at a rate of about 300° C./min (the first heat treatment step). Then, the cooled material is cold-rolled down to a thickness of 0.3 mm (the second cold rolling step), and then heated at 470° C. for 2 hours (the second heat treatment step) (Sample No. 1).

Sample No. 1 thus made is measured in relation to the properties of tensile strength, yield strength, elongation and electric conductivity. The tensile strength, yield strength and elongation are measured based on JIS Z 2241 and the electric conductivity is measured based on JIS H 0505. The measurement results are shown in Table 2.

As shown in Table 2, it is confirmed that Sample No. 1 has good properties, i.e., a tensile strength of 740 N/mm², a yield strength of 684 N/mm², an elongation of 12% and an electric conductivity of 42% IACS, which are suited to the object of the invention.

Examples 2 to 9 (=Sample Nos. 2 to 9)

Copper alloys with compositions as Sample Nos. 2 to 9 in Table 1 are cast like Example 1 (=Sample No. 1), rolled into samples with a thickness of 0.3 mm in the same processes as Example 1 (=Sample No. 1), subjected to the second heat treatment (to be kept at 470° C. for 2 hours) like Example 1 (=Sample No. 1). Sample Nos. 2 to 9 are measured in relation to the properties of tensile strength, yield strength, elongation and electric conductivity like Example 1 (=Sample No. 1). The measurement results are shown in Table 2.

As shown in Table 2, it is confirmed that Sample Nos. 2 to 9 have good properties suited to the object of the invention. Further, it is confirmed that Sample Nos. 6 to 9, each of which contains 0.1 mass % of Mg, Ti, Cr or Zr in addition to the composition of Sample No. 1, all have a tensile strength and yield strength higher than Sample No. 1 and that, thus, the additive elements are effective.

Sample No. 4, which is slightly lower than the more preferred composition ratio described earlier in relation to the Ni content, Si content and the total content of Fe and Co, has a tensile strength and yield strength slightly lower than Sample No. 1 while it has an elongation and electric conductivity higher than Sample No. 1.

Sample No. 5, which is slightly higher than the more preferred composition ratio described earlier in relation to the Ni content, has an elongation and electric conductivity slightly lower than Sample No. 1 while it has a tensile strength and yield strength higher than Sample No. 1.

However, it is confirmed that both of Sample Nos. 4 and 5 can sufficiently secure the expected effects (i.e., a tensile strength of 700 N/mm² or more, a yield strength of 650 N/mm² or more, an elongation of 10% or more, and an electric conductivity of 40% IACS or more).

Comparative Examples 1 to 13 (=Sample Nos. 10 to 22)

The reasons for defining the alloy composition in the copper alloy material of the invention are described below as compared with Comparative examples 1 to 13.

Copper alloys with compositions as Sample Nos. 10 to 22 (which correspond to Comparative examples 1 to 13, respectively) in Table 1 are cast like Example 1 (=Sample No. 1), rolled into samples with a thickness of 0.3 mm in the same processes as Example 1 (=Sample No. 1), subjected to the second heat treatment (to be kept at 470° C. for 2 hours) like Example 1 (=Sample No. 1).

Sample Nos. 10 to 22 obtained are measured in relation to the properties of tensile strength, yield strength, elongation and electric conductivity like Example 1 (=Sample No. 1). The measurement results are shown in Table 2.

Sample Nos. 10 to 15 are out of the invention-defined range in relation to the content of Ni and Si. In Sample Nos. 10 and 14, a crack is observed in the ingot since the content of Si is too large. In Sample No. 12, due to the excessive content of Ni, the electric conductivity is degraded even though the tensile strength is high. In Sample Nos. 11, 13 and 15, where one or both of the Ni and Si contents is too small, the sufficient tensile strength cannot be obtained.

In Sample No. 16, the amount of P is excessive. In this case, a crack is observed in the ingot like the case of excessive content of Si (Sample Nos. 10 and 14). In Sample No. 17, the amount of Fe and Co is excessive. In these cases, the electric conductivity is degraded even though the tensile strength is high.

Sample Nos. 18 and 19 are out of the invention-defined range in relation to the ratio, (Ni+Fe+Co)/(Si+P), of the total mass of Ni, Fe and Co and the total mass of Si and P. In Sample No. 18 that the ratio is smaller than the invention-defined range, the electric conductivity is degraded and both the tensile strength and yield strength are not high. Similarly, in Sample No. 19 that the ratio is larger than the invention-defined range, the electric conductivity is degraded and both the tensile strength and yield strength are not high.

In Sample No. 20, the content of Sn is excessive. In Sample No. 21, the content of Zn is excessive. In both cases, the electric conductivity is degraded even though the tensile strength is high. In Sample No. 22, the content of Mg is excessive. In this case, the electric conductivity is deteriorated and the elongation is not high. TABLE 1 Composition (mass %) (Ni + Fe + Co)/ Kind Sample No. Ni Si P Fe Co Sn Zn Other Cu (Si + P) ratio Example 1 1 3.0 0.5 0.15 0.15 0.15 1.0 1.5 — balance 5.1 2 2 3.0 0.5 0.15 0.3 — 1.0 1.5 — balance 5.1 3 3 3.0 0.5 0.15 — 0.3 1.0 1.5 — balance 5.1 4 4 2.0 0.3 0.1 0.1 0.1 1.0 1.5 — balance 5.5 5 5 4.0 0.6 0.2 0.2 0.2 1.0 1.5 — balance 5.5 6 6 3.0 0.5 0.15 0.15 0.15 1.0 1.5 0.1Mg balance 5.1 7 7 3.0 0.5 0.15 0.15 0.15 1.0 1.5 0.1Ti balance 5.1 8 8 3.0 0.5 0.15 0.15 0.15 1.0 1.5 0.1Cr balance 5.1 9 9 3.0 0.5 0.15 0.15 0.15 1.0 1.5 0.1Zr balance 5.1 Comparative 1 10 8.0 1.4 0.2 0.15 0.15 1.0 1.5 — balance 5.2 example 2 11 0.5 0.1 0.05 0.15 0.15 1.0 1.5 — balance 5.3 3 12 8.0 0.8 0.2 0.15 0.15 1.0 1.5 — balance 8.3 4 13 0.5 0.3 0.05 0.5 0.5 1.0 1.5 — balance 4.3 5 14 5.0 1.2 0.15 0.5 0.5 1.0 1.5 — balance 4.4 6 15 1.5 0.1 0.1 0.1 0.1 1.0 1.5 — balance 8.5 7 16 4.0 0.5 0.5 0.15 0.15 1.0 1.5 — balance 4.3 8 17 3.0 0.5 0.15 1.0 1.0 1.0 1.5 — balance 7.7 9 18 1.5 0.5 0.15 0.1 0.05 1.0 1.5 — balance 2.5 10 19 4.0 0.3 0.1 0.4 0.4 1.0 1.5 — balance 12.0 11 20 3.0 0.5 0.15 0.15 0.15 4.0 1.5 — balance 5.1 12 21 3.0 0.5 0.15 0.15 0.15 1.0 8.0 — balance 5.1 13 22 3.0 0.5 0.15 0.15 0.15 1.0 1.5 2.0Mg balance 5.1

TABLE 2 Tensile Electric Sample Crack of strength Yield strength Elongation conductivity Kind No. ingot (N/mm²) (N/mm²) (%) (% IACS) Example 1 1 no 740 684 12 42 2 2 no 736 678 12 42 3 3 no 738 680 12 42 4 4 no 708 654 14 44 5 5 no 772 720 10 41 6 6 no 760 706 12 42 7 7 no 776 724 12 41 8 8 no 755 696 12 42 9 9 no 752 694 12 42 Comparative 1 10 found — — — — example 2 11 no 518 470 14 55 3 12 no 734 670 8 33 4 13 no 580 528 12 40 5 14 found — — — — 6 15 no 588 536 14 42 7 16 found — — — — 8 17 no 752 690 10 36 9 18 no 574 524 14 38 10 19 no 654 602 8 30 11 20 no 778 722 10 33 12 21 no 764 710 10 33 13 22 no 780 726 8 35

Comparative Examples 14 to 19 (=Sample Nos. 23 to 28)

The reasons for defining the conditions in the method of making the copper alloy material of the invention are described below as compared with Comparative examples 14 to 19.

Sample Nos. 23 to 28 (which correspond to Comparative examples 14 to 19, respectively) are made such that the copper alloys with the same composition as Sample No. 1 in Example 1 are processed in similar processes to Example 1, where the thickness ratio of the cold-rolled material in the first cold rolling step and the final product, and the heating conditions of the first and second heat treatment steps are shown in Table 3.

Sample Nos. 23 to 28 obtained are measured in relation to the properties of tensile strength, yield strength, elongation and electric conductivity like Example 1 (=Sample No. 1).

Further, a bending test is conducted to evaluate the bending workability. The bending test is based on a W-bending test as set forth in JIS H 3110 and is conducted such that the sample is bent at an angle of 90 degrees with a bend radius of 0 mm and then the surface of bent portion is observed to check the existence of a crack. In detail, the bending test is conducted in both cases that the direction of bending axis is orthogonal to the rolling direction, and that the direction of bending axis is parallel to the rolling direction. Here, when no crack formation is observed in both directions (i.e., not depending on the rolling direction), the sample is evaluated matter as “Good”. When a crack formation is observed in either direction, the sample is evaluated as “Not good”. The measurement/observation results are shown in Table 4.

It is confirmed that Sample No. 1 (=Example 1) can have a high tensile strength of more than 700 N/mm², a high yield strength of more than 650 N/mm² , a good elongation of more than 10% and a good electric conductivity of more than 40% IACS as well as good bending workability, while Sample Nos. 23 to 28 (=Comparative examples 14 to 19) are significantly insufficient in either of the tested properties (i.e., tensile strength, yield strength, elongation, electric conductivity and bending workability).

Sample Nos. 23 and 24 are out of the invention-defined range in relation to the thickness ratio between the cold-rolled material in the first cold rolling step and the final product. If the cold-rolled material in the first cold rolling step is too thin (i.e., the thickness ratio is less than 1.1) (Sample No. 23), the defects introduced in the second cold rolling step is reduced and, therefore, the yield strength of the final product remains low and the tensile strength is also low. By contrast, if the cold-rolled material in the first cold rolling step is too thick (i.e., the thickness ratio is more than 1.3) (Sample No. 24), the defects introduced in the second cold rolling step is excessive and, therefore, the elongation of the final product is degraded and anisotropy in the bending appears to deteriorate the bending workability (i.e., a crack is formed when the sample is bent with the bending axis parallel to the rolling direction).

Sample Nos. 25 and 26 are out of the invention-defined range in relation to the heating temperature of the first heat treatment step. If the heating temperature is too low or high, both the tensile strength and the yield strength are low. If the heating temperature is too high (Sample No. 26), the elongation, the electric conductivity and the bending workability are low as well as the tensile strength and the yield strength.

Sample Nos. 27 and 28 are out of the invention-defined range in relation to the heating temperature of the second heat treatment step. If the heating temperature is too low (Sample No. 27), the electric conductivity is low, the tensile strength, the yield strength and the elongation are insufficient, and the bending workability is lowered. If the heating temperature is too high (Sample No. 28), the tensile strength and the yield strength are insufficient even though the electric conductivity is high. TABLE 3 Thickness ratio of first cold-rolled material and First heat treatment Second heat treatment kind Sample No. final product heating conditions heating conditions Remarks Example 1 1 1.20:1 800° C. × 10 min 470° C. × 2 h — Comparative 14 23 1.07:1 800° C. × 10 min 470° C. × 2 h Same example composition as No. 1 15 24 1.67:1 800° C. × 10 min 470° C. × 2 h Same composition as No. 1 16 25 1.20:1 600° C. × 10 min 470° C. × 2 h Same composition as No. 1 17 26 1.20:1 950° C. × 10 min 470° C. × 2 h Same composition as No. 1 18 27 1.20:1 800° C. × 10 min 350° C. × 2 h Same composition as No. 1 19 28 1.20:1 800° C. × 10 min 550° C. × 2 h Same composition as No. 1

TABLE 4 Tensile strength Yield strength Elongation Electric conductivity Bending Kind Sample No. (N/mm²) (N/mm²) (%) (% IACS) workability Example 1 1 740 684 12 42 Good Comparative 14 23 670 558 16 40 Good example 15 24 750 688 9 43 Not good 16 25 574 504 12 42 Good 17 26 688 630 8 36 Not good 18 27 590 532 8 33 Not good 19 28 578 510 14 44 Good

Although the invention has been described with respect to the specific embodiments for complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth. 

1. A copper alloy material for electric parts, comprising: 1.0 to 5.0 mass % of Ni; 0.2 to 1.0 mass % of Si; 0.05 to 2.0 mass % of Sn; 0.1 to 5.0 mass % of Zn; 0.01 to 0.3 mass % of P; 0.05 to 1.0 mass % of at least one of Fe and Co; and the balance consisting of Cu and an unavoidable impurity, wherein a ratio, (Ni+Fe+Co)/(Si+P), between a total mass of Ni, Fe and Co and a total mass of Si and P is 4 or more and 10 or less.
 2. The copper alloy material according to claim 1, wherein: the copper alloy material comprises a tensile strength of 700 N/mm² or more.
 3. The copper alloy material according to claim 1, wherein: the copper alloy material comprises an elongation of 10% or more.
 4. The copper alloy material according to claim 1, wherein: the copper alloy material comprises an electric conductivity of 40% IACS or more.
 5. A copper alloy material for electric parts, comprising: 1.0 to 5.0 mass % of Ni; 0.2 to 1.0 mass % of Si; 0.05 to 2.0 mass % of Sn; 0.1 to 5.0 mass % of Zn; 0.01 to 0.3 mass % of P; 0.05 to 1.0 mass % of at least one of Fe and Co; 0.01 to 1.0 mass % of at least one of Mg, Ti, Cr and Zr and the balance consisting of Cu and an unavoidable impurity, wherein a ratio, (Ni+Fe+Co)/(Si+P), between a total mass of Ni, Fe and Co and a total mass of Si and P is 4 or more and 10 or less.
 6. The copper alloy material according to claim 5, wherein: the copper alloy material comprises a tensile strength of 700 N/mm² or more.
 7. The copper alloy material according to claim 5, wherein: the copper alloy material comprises an elongation of 10% or more.
 8. The copper alloy material according to claim 5, wherein: the copper alloy material comprises an electric conductivity of 40% IACS or more.
 9. A method of making the copper alloy material for electric parts as defined in claim 1, comprising: preparing a copper alloy raw material with the same composition and the same mass ratio as defined in claim 1; a first cold rolling step that the copper alloy raw material is cold-rolled down to a thickness of 1.1 to 1.3 times a target thickness of a final product; a first heat treatment step that the cold-rolled material in the first cold rolling step is heated up to 700 to 850° C. and then cooled to 300° C. or less at a cooling rate of 25° C./min or more; a second cold rolling step that the treated material in the first heat treatment step is cold-rolled down to the target thickness; and a second heat treatment step that the cold-rolled material in the second cold rolling step is heated up to 400 to 500° C. and held for 30 min. to 3 hrs.
 10. A method of making the copper alloy material for electric parts as defined in claim 5, comprising: preparing a copper alloy raw material with the same composition and the same mass ratio as defined in claim 5; a first cold rolling step that the copper alloy raw material is cold-rolled down to a thickness of 1.1 to 1.3 times a target thickness of a final product; a first heat treatment step that the cold-rolled material in the first cold rolling step is heated up to 700 to 850° C. and then cooled to 300° C. or less at a cooling rate of 25° C./min or more; a second cold rolling step that the treated material in the first heat treatment step is cold-rolled down to the target thickness; and a second heat treatment step that the cold-rolled material in the second cold rolling step is heated up to 400 to 500° C. and held for 30 min. to 3 hrs. 